High temperature terminal connector for radiant heater elements



Feb. 6, 1940. F. A. SIMONS 2,139,231

HIGH TEMPERATURE TERMINAL CONNECTOR FOR RADIANT HEATER ELEMENTS Filed April 17, 1939 j; 1017 7 r //.9 j 1e wamxxmmmw fig : 2 v A 55 55 xx 35 29 fza .?2 f I? 15; 51 2: y J

Z6 m )f [.10 11 V ///X/ 12 Y INVENTOR #006 14, 5/07005 ATTORNEYS Patented Feb. 6, 1940 UNITED STATES PATENT OFFICE HIGH TEMPERATURE TERMINAL CONNEC- TOR FOR RADIANT HEATER ELEMENTS Application April 17, 1939, Serial No. 268,261

4 Claims.

The invention relates to high temperature terminal connections for radiant heater elements. and particularly for such elements which are adapted to operate at temperatures up to 1250 C.

The development of silicon carbide resistor bars for heating purposes has made available radiant heating means of great industrial importance. As usually constructed, the radiant portion of such a bar is commercial silicon carbide, fused at each end to a re atively short contact member composed of silicon carbide and powdered metal to serve as a better conductor and to keep the ends of the bar relativelv cool. In operation, electrical contact is made to composite bars at each end throu h a series of touching but independent links of metal held in contact with one another and with the heater bar by means of pressure exerted by a spring which rests on a fixed base plate. Radiation occurs only from the central portion of the heater consisting of the silicon carbide bar. Such heaters, and especially the terminal portions thereof. cannot operate under conditions of complete immersion in a molten bath as the terminal connections will not stand up under such high temperature conditions. Another disadvantage which has been observed frequently is that the composite bars, having silicon carbide and metal composition ends, break easily under operating conditions at or near the point at which the composition is fused to the silicon carbide resistor element.

Radiant heaters capable of operating at or up to about 1250 C. are of great importance in the fusion and alloying of metals such as aluminum which is usually handled in graphitelined steel equipment which has such poor thermal conductivity it cannot be heated economically from without. It is desired to have such a heater which can operate at full immersion in the heated bath, and which will be radiant over its entire length. It is also desired to minimize expense due to broken silicon carbide heater bars by employing the central resistor portion having broken ends in a practical mechanical and electrical set-up such that the bar can operate at full heat throughout its length. Such means have not been available heretofore.

It is accordingly among the objects of theneath the surface of the bath being heated. It is another object to provide such a terminal connector which will engage with either the original or a broken end of a resistor bar. Other objects and advantages will appear as the description l proceeds.

To the accomplishment of the foregoing and related objects, the invention, then, consists of the means hereinafter fully described and pointed out in the claims, the annexed drawing and the following description setting forth in detail certain means for carrying out the invention, such disclosed means illustrating, however, but one of various ways in which the principle of the invention may be used.

In the said annexed drawing:

Fig. 1 is a longitudinal section through a terminal connector showing its use on a broken resistor bar.

Figs. 2 and 3 show typical shapes of commer- 2 cially available silicon carbide resistor bars.

Fig. 4 is a vertical section through a molten bath heated with a submerged resistor bar electrically connected to a source of current through terminal connectors of the type shown in Fig. 1.

Fig. 5 is a vertical section through a boiler heated by means of a resistor bar fitted with terminal, connectors shown in Fig. 1.

According to the invention, a terminal connec tor for radiant heaters adapted to use on whole or on broken ends of the heating element and capable of operating at radiant heat and under conditions of full immersion may consist in or comprise an internally threaded thimble and enaging male compression member bored axially through its length to receive the end of a resistor bar, the thimble and compression member being constructed of a material such as stainless steel which will withstand the temperatures encountered in operation. The space within the thimble, beyond the end of the compression member, is filled with an electrically conducting material, preferably in granular or powdered form, and having a fusion point higher than that to which the terminal will be subjected when in operation. The new terminal connector is further equipped with means for bringing the resistor element into electrical communication with a source of current.

Referring now to the drawing, wherein like parts are designated by like numerals in the 56' various figures, a thimble III is internally threaded adjacent its rim to receive a male compression member l2, the shank of which is threaded to engage the threads H in the thimble Ill. The compression member I2 is bored axially through its length and of sumcient caliber to receive a silicon carbide or like resistor bar l3 without seizing, centering ring 21 being provided to center the bar and to provide a slight space H to prevent arcing between the bar l3 and compression member I2. The base of the thimble l0, beyond the end of the male compression member I2, is filled with a granular or powdered material l5 of fair electrical conductivity capable of withstanding temperatures to which the connectormay be subjected in use. As the compression member I2 is screwed into position around a resistor bar l3. the granular conducting material I5 is compressed and seizes the resistor bar l3, holding it firmly and providing electrical communication between it and the thimble [0. The thimble It may be drilled and tapped to provide threaded sockets l6 for receiving lugs or bolts whereby electrical communication may be hadwith a cable, bus-bar, or like conducting means I! and thence with a source l8 of current.

A preferred embodiment of the male compression member I2 is shown in Fig. 1 where the distal tip 26 of said member is bevelled away from the resistor bar l3. In this form, when the compression member is screwed into thimble l0 and comes in contact with the granular material I5, the latter is compressed between the tip 26 and the end 20 of bar l3, seizing the bar and holding the compression member in fixedspace relation thereto substantially without frictional engagement between the said bar l3 and compression member l2. Although other modifications of the tip 26 of compression member [2 may be employed without departing from the scope of the invention, it is believed that the form illustrated in Fig. I is most practical.

In practice, a silicon carbide resistor l3 of either of the typical shapes shown in Figs. 2 and 3 and having conducting tips l9 fused thereto, or a bar having a broken end 20 as illustrated in Fig. 1; isinserted through the compression gland member l2 and seated in the conducting material I 5 in the cavity of thimble Ill. The compression member I 2 is fitted into threads H and tightened down to compress the granular conducting material l5, thereby to hold bar l3 securely in place without pinching or crimping the same. An electrical cable I! is attached to thimble l0 suitably through bolts or lugs fitted into the tapped sockets l6. Similar connection is made with a terminal connector at the other end of the resistorbar. The so-connected bar may be mounted as in a pipe 2| and supported in rings 22 suitably of alundum or similar heat-resistant composition. Another pipe 23 vertical to pipe 2| and serving as a conduit for electrical cables I! may be made part of the system, and the so-encased heater mounting submerged as in a bath 24 of molten material contained in any suitable vessel 25. When brought to operating temperature, the bar l3 expands and the attached terminal connectors l0 ride back and forth, as required by temperature changes, on the rings 22 through the pipe 2|.

Another way in which the heater and high temperature terminals may be employed is to mount them as shown in Fig. 5 wherein the resistor and terminals are mounted in the vertical fire tube of a boiler, heat being radiated to the fluid in the boiler.

Other practical applications of the high temperature terminals herein-described will become apparent to those carrying out such high temperature operations as may require silicon carbide resistance heaters.

The contacting material used as a conductor H5 in the thimbles l0 may be any finely divided granular or powdery material of fair electrical conductivity which will withstand the temperatures of operation without fusion, and as examples may be mentioned iron or steel filings, partially oxidized iron, graphite dust, and mixtures of these materials.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism hereindisclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

1. As a terminal connector for radiant heater bars, the combination of a thimble internally threaded adjacent its rim, a male compression member threaded on its shank to engage the said internal threads of the thimble, and bored axially of suflicient caliber through its length to receive a resistor bar without seizing, and electrically conducting granular or powdered material within the thimble which has a fusion point higher than that to which the terminal will be subjected in use and which is compressible to engage and hold the end of a resistor bar when the shank of the male compression member is screwed into the thimble.

2. As a terminal connector for radiant heater bars, the combination of a thimble internally threaded adjacent its rim, a male compression member threaded on its shank to engage the said internal threads of the thimble, and bored axially and hold the end of a resistor bar when the said compression member is screwed into the thimble.

3. In a radiant heater assembly, the combination of a radiant heater bar, over the end of" the said bar a male compression member the distal I end of which is directed toward the end of the heater bar, the said compression member being externally threaded near the proximal end of its shank and'bored axially through its length and provided internally near its distal tip with a I centering ring to receive and center the said resistor bar without seizing, a thimble internally threaded adjacent its rim to engage the threads 01' the said compression member and containing a granular or powdered material of fair electrical conductivity which has a fusion point higher than that to which the terminal will be subjected when in use and which is compressible to engage and hold the end of the resistor bar when the thimble and compression member are screwed together, and on the said thimble means for effecting electrical communication with a source of current.

4. The combination of the terminal connector, recited in claim 2 and a silicon carbide radiant heater bar inserted through the shankof the compression member and held in place by the granular or powdered material in the thimble of the connector when the latter is compressed.

. FRANK A. SIMONS. 

